This application relates to co-pending application entitled xe2x80x9cAPPARATUS AND METHOD FOR USING ORTHOGONALLY POLARIZED LIGHT IN PROJECTION COCKPIT DISPLAYSxe2x80x9d filed on even date herewith by the same inventor and assigned to a common assignee.
The present invention generally relates to projection cockpit displays, and even more particularly relates to such displays having multiple sources of illumination.
In the past, designers of avionics displays have endeavored to provide projection displays with ever-increasing image quality, reliability, and economic efficiency. Projection displays generally use a single, broad-spectrum white light source to illuminate an image generating system. These lamps are often high-intensity, high-efficiency incandescent or discharge-type lamps that have lifetimes of less than 5000 hours. Reliance on such single short-lifetime lamps makes projection displays difficult to deploy in an avionics environment in an economically efficient manner. Other lamps with longer lifetimes have been used, but they often generate a white light, which has a deficiency at one or more wavelengths in the needed spectrum. To address these deficiencies, lamps with increased overall output may be used, so that the areas of relative deficiency exceed the minimum threshold. However, in such cases, other wavelengths output too much light, which then requires color filters to be employed to attenuate certain wavelengths. This attenuation results in inefficiencies because more light than is needed is generated and then discarded. This results in undesirable amounts of heat being generated and power being consumed.
Consequently, there exists a need for improvement in illumination of projection displays.
It is an object of the present invention to provide projection displays having a superior image luminance characteristic.
It is a feature of the present invention to utilize multiple light sources for a single projection display area.
It is an advantage of the present invention to provide increased optical output power than is feasible with single sources.
It is another feature of the present invention to utilize multiple light sources which may use differing technologies or designs.
It is another advantage of the present invention to utilize different light source technologies under different display operating conditions.
It is another feature of the present invention to utilize a light flux integrator.
It is another advantage of the present invention to optically combine light from multiple light sources into a single output.
It is another advantage of the present invention to have high efficiency of light coupling between sources and displays.
It is another advantage of the present invention to have a rugged light collection and integration system.
It is another object of the present invention to provide projection displays having a superior image spectral characteristic.
It is another feature of the present invention to include a plurality of light sources which may have spectrally complementary characteristics.
It is another advantage of the present invention to reduce unevenness in power distribution across the spectral range.
It is another advantage of the present invention to provide different source spectra during different modes of display operation.
It is another object of the present invention to provide projection displays having a superior lamp replacement or maintenance characteristic.
It is another feature of the present invention to include redundant light sources used in a simultaneous manner.
It is another advantage of the present invention to provide a fail operational projection display wherein the display remains useful after failure of one or more sources.
It is another feature of the present invention to use multiple light sources in a sequential manner.
It is another advantage of the present invention to provide for extended service life of an avionics projection display lamp system.
It is another feature of the present invention to use multiple light sources in a complex combination of sequential and simultaneous operation.
It is another advantage of the present invention to provide for an extended image luminance dimming range.
The present invention is an apparatus and method for illuminating projection displays, which are designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features, and achieve the already articulated advantages. The present invention reduces maintenance time wasted in repeatedly changing short lifetime lamps. Similarly, the amount of excess light and heat that is generated when color filters are used to affect spectral deficiencies is also reduced.
Accordingly, the present invention is a projection display system which utilizes a multi-lamp architecture where light from these multiple lamps is integrated to illuminate one projection display system.